Microsoft’s TV platform has a rocky history. Not only has it been blamed for much of AT&T’s slow U-verse rollout, but some elements have reportedly been so bloated that Verizon found itself rewriting code last year to stay on its FiOS schedule. This after the software giant spent years trying unsuccessfully to muscle its way into the cable industry. So on Mon, Microsoft unveiled a new version of the platform’s IPTV Edition to be rebranded as "Microsoft Mediaroom," which touts new multimedia features such as in-home personal music and photo sharing, and dynamic MultiView (multiple picture-in-picture) capabilities. But perhaps most significant is a new "Multimedia Application Environment," which opens Microsoft’s platform to service providers and other 3rd party developers seeking to write custom IPTV apps (i.e., dynamic VOD portals, casual gaming, etc). Microsoft obviously has much experience working with software developers, at least in the PC space. "In the highly competitive television market, a well-regarded brand can be a very strong asset," said Christine Heckart, gm of worldwide marketing for Microsoft TV. Still unclear is whether Microsoft’s Mediaroom push will help the telcos gain ground against entrenched cable operators, most of which have yet to embrace the IPTV architecture. – Meanwhile, Microsoft on Mon also launched its new MSN Mobile portal in an effort to improve navigation and other MSN.com features when used on mobile devices. And just in time for Apple’s iPhone debut next week.